1. Field of the Invention
This invention relates to drag reducing agent slurries, and in particular, drag reducing agent slurries having alfol alcohols used in methods for improving flow of hydrocarbons through conduits, particularly pipelines. The invention also relates to methods for making drag reducing agent slurries.
2. Description of Related Art
Generally speaking, the flow of liquid in a conduit, such as a pipeline, results in frictional energy losses. As a result of this energy loss, the pressure of the liquid in the conduit decreases along the conduit in the direction of the flow. For a conduit of fixed diameter, this pressure drop increases with increasing flow rate. When the flow in the conduit is turbulent (Reynold's number greater than about 2100), certain high molecular weight polymers can be added to the liquid flowing through the conduit to reduce the frictional energy losses and alter the relationship between pressure drop and flow rate. These polymers are sometimes referred to as drag reducing agents (“DRAs”), and they interact with the turbulent flow processes and reduce frictional pressure losses such that the pressure drop for a given flow rate is less, or the flow rate for a given pressure drop is greater. Because DRAs reduce frictional energy losses, increase in the flow capability of pipelines, hoses and other conduits in which liquids flow can be achieved. DRAs can also decrease the cost of pumping fluids, the cost of equipment used to pump fluids, and provide for the use of a smaller pipe diameter for a given flow capacity.
One type of drag reducing agent presently utilized is a slurry. Drag reducing agent slurries are those formed by polymerizing monomers, preferably alpha olefin monomers, to form polymers that are subsequently ground to a small size and suspended in a liquid vehicle, i.e. suspending agent. Drag reducing agent slurries facilitate the rapid dispersion of the drag reducing agent through out the hydrocarbon being transported through a conduit. While various polymerization methods, reactants, partitioning agents, and slurries have been published in the patent literature, many of those methods include components of drag reducing agent slurries that increase the cost of production of the drag reducing agents slurry. Further, some components of drag reducing agent slurries cannot be removed from the hydrocarbon after they have been introduced into the conduit. In many, if not all instances, these slurry components remaining in the hydrocarbon foul the hydrocarbon in the conduit, thereby decreasing the number of uses of the hydrocarbon and/or the effectiveness of the use of the hydrocarbon.
Generally, water soluble alcohols, water, glycols, glycerin, and water/water-soluble alcohol mixtures (referred to herein as “water-alcohol mixtures”) are known in the art as being suspending materials. All of these prior attempts have shortcomings. For example, the addition of water poses serious implications as it relates to water contamination, i.e., hazing, of motor fuel, e.g., gasoline, diesel, and kerosene, in pipelines. Other significant problems associated with the inclusion of water in the drag reducing agent slurries include additional wastewater generation, thereby requiring disposal, increased systems corrosion, increased biological activity in “free-water” fallout areas within the pipeline and terminal storage tanks.
In other prior drag reducing agent slurries, small amounts of polar and/or other water soluble alcohols have been linked with serious biological upsets and resulting operational problems due, in part, to food to microorganism balances, undesirable biological facilitation, excessive biological oxygen demand and chemical oxygen demand loading, and bio-mass bulking within various refineries' activated sludge processes. These refineries depend on activated sludge processes as the most practical and efficient means of treating wastewater received and generated within the refining processes prior to its reintroduction, or discharge outside of, the refineries. In fact, some refineries have set strictly enforced limits on drag reducing agents slurries containing water soluble alcohols, glycols, and glycerins received into their refineries from crude oil pipelines.
Additionally, the inclusion of water, glycols, glycerin, and water-alcohol mixtures as a part of, or as the entire, suspending agent, generally requires the inclusion of other components, thereby increasing the cost of formation of the drag reducing agent, increasing potential harm to refineries, and increasing cost of refining the hydrocarbon due to the cost of removal and disposal of these additives. For example, surfactants, e.g., nonylphenol ethyoxylate, alkaline metal stearates, e.g., magnesium stearate and calcium stearate used as partitioning agents to reduce the potential of the finely ground polymer solids from re-agglomerating and thus destabilizing the drag reducing agent slurry, and biocides are included in some prior drag reducing agent slurries. Some refineries have prohibited the use of drag reducing agent slurries containing surfactants and metal stearates in their crude oil pipeline because, upon entering the refining facilities, the surfactants and alkaline metal stearates are believed to be responsible for upset the refining process, including the refineries vital desalting processes.
Siloxane containing antifoams are also usually included in prior drag reducing agent slurries to reduce or eliminate the potential of foaming within the end user's pipeline system following the addition of drag reducing agent slurry. Siloxane containing antifoams are objectionable components because they are believed to be responsible for causing deleterious effects on various refining processes and facilitate fouling within the refining process.
Generally, all of these additional components are insoluble contaminants in the hydrocarbon stream in the pipeline. Such contaminants are undesirable and the art has continually sought a drag reducing agent slurry that excludes these undesirable components.
Another disadvantage of the prior drag reducing agent slurries is that the “shelf-life” of these drag reducing agent slurries are extremely short and they require storage within strict temperature ranges. For example, one prior drag reducing agent slurry containing water and water-alcohol mixtures as the suspending agent requires its storage to be within expensive temperature controlled housing/containment, or container/building, to help insure its usability and stability, (i.e. between 35–85° F.). Without proper temperature control in such a storage facility this prior drag reducing agent slurry becomes frozen at or near the freezing point of water, or microbiologically decomposes and destabilizes/ferments in an unacceptably short time as ambient temperatures move above 90° F. As known to persons skilled in the art, a large portion of crude oil is produced in extremely hot regions of the world, e.g., Saudi Arabia, Venezuela, Texas, Mexico, and Gulf of Mexico, and extremely cold regions of the world, e.g., Alaska, Siberia, and Canada. Accordingly, these prior drag reducing agent slurries are not suitable for use in these environments without additional storage facilities.
Another shortcoming of prior drag reducing agent slurries is that the polymer load per gallon, i.e., the amount of active polymer that can be suspended in a gallon of suspending agent without the polymer particles re-agglomerating, is limited. Applicants are unaware of any drag reducing agent slurry that contains greater than about 2.0 pounds of this polymer per gallon of suspending material. Addition of polymer in amounts greater than about 2.0 pounds of polymer per gallon results in an extremely viscous and unstable drag reducing agent slurry. The ability to increase the polymer solids as a ratio to the total weight of the slurry offers improved treating performance, better logistical benefits and lower logistical and capital costs.
Still another shortcoming of prior drag reducing agent slurries is that the drag reducing agent slurry is not capable of being “re-suspended” should the polymer “separate” from its suspending material. As prior drag reducing agent slurries age, the polymer has a tendency to separate by settling to the bottom or rising to the top of the tank, or other container, containing the drag reducing agent slurry. When this occurs, the polymer further re-agglomerates and cannot be “re-suspended.” As such, the drag reducing agent slurry is of no value and new, or “fresh” drag reducing agent slurry is required.
Additionally, none of the prior attempts provide the surprisingly unexpected results of using the suspending materials of the present invention. For instance, the suspending materials of the present invention provide a drag reducing agent slurry that has an increased shelf life, a minimal impact on pipeline and refinery operations, and permit formation of a drag reducing agent slurries having more active polymer per gallon than any other prior drag reducing agent slurries.
Accordingly, prior to the development of the present invention, there has been no drag reducing agent slurry, process for forming a drag reducing agent slurry, or process for reducing drag in a conduit, which: does not negatively impact wastewater treatment facilities; permits longer term storage without biological degradation and temperature destabilization; does not insult motor fuels and other refined products; reduces instances of re-agglomeration; and provides a more stable drag reducing agent slurry during production, transportation, storage, and use. Therefore, the art has sought a drag reducing agent slurry, process for forming a drag reducing agent slurry, and process for reducing drag in a conduit, which: does not negatively impact wastewater treatment facilities; permits longer term storage without biological degradation and temperature destabilization; does not insult motor fuels and other refined products; reduces instances of re-agglomeration; and provides a more stable drag reducing agent slurry during production, transportation, storage, and use.
While various components of drag reducing slurries have been used in connection with certain drag reducing agents, the inventors are not aware of any patents or publications showing alfol alcohols being used as a component of drag reducing agent slurries. For example, U.S. Pat. Nos. 6,172,151; 5,244,937; 5,449,732; 5,504,131; 5,504,132; and 5,539,044 disclose certain components of drag reducing agent slurries, but do not disclose or suggest the alfol alcohols as a component of drag reducing agent slurries.